Sync presentation

[james-d-mitchell]

This PR adds support for 3 helper functions from libsemigroups that were not supported before. I think this means that all helper functions that we want to support from presentation are now supported.

[Joseph-Edwards]

This all looks good to me, mod the removal of the empty line that cpplint is complaining about.

A few of our recent PRs have been introducing whitespace/formatting changes on otherwise unchanged lines. This is fine for this PR, but we should probably discuss and settle on a common formatter to avoid this moving forward.

[james-d-mitchell]

This all looks good to me, mod the removal of the empty line that cpplint is complaining about.

A few of our recent PRs have been introducing whitespace/formatting changes on otherwise unchanged lines. This is fine for this PR, but we should probably discuss and settle on a common formatter to avoid this moving forward.

Agreed, one or the other of us is using the wrong thing to format the files, and we are cycling back and forth between the differences.